Thin film photovoltaic (PV) modules (also referred to as “solar panels”) based on cadmium telluride (CdTe) paired with cadmium sulfide (CdS) as the photo-reactive components are gaining wide acceptance and interest in the industry. CdTe is a semiconductor material having characteristics particularly suited for conversion of solar energy to electricity. For example, CdTe has an energy bandgap of about 1.45 eV, which enables it to convert more energy from the solar spectrum as compared to lower bandgap semiconductor materials historically used in solar cell applications (e.g., about 1.1 eV for silicon). Also, CdTe converts radiation energy in lower or diffuse light conditions as compared to the lower bandgap materials and, thus, has a longer effective conversion time over the course of a day or in cloudy conditions as compared to other conventional materials. The junction of the n-type layer and the p-type layer is generally responsible for the generation of electric potential and electric current when the CdTe PV module is exposed to light energy, such as sunlight. Specifically, the cadmium telluride (CdTe) layer and the cadmium sulfide (CdS) form a p-n heterojunction, where the CdTe layer acts as a p-type layer (i.e., an electron accepting layer) and the CdS layer acts as a n-type layer (i.e., an electron donating layer).
The photovoltaic modules are typically deployed in the field by connected a plurality of modules in series to form a “string” of PV modules. The fewer strings that can be used, the lower the total balance of the system costs. However, the number of solar modules in each string is limited in total voltage per string. With respect to CdTe PV modules, which have relatively high voltage per cell due to the relatively high band gap of CdTe, fewer modules can be linked together in each string than may be desired.
Thus, a need exists for photovoltaic modules having lower voltages, particularly with respect to CdTe photovoltaic devices.